The virus has taken different paths in different countries. Some of the reason may be due to actions taken in terms of tracing and quarantine procedures, but for future reference, it is important to distinguish which were more effective than others. Factors additional to pathogen exposure can also affect whether an infection takes hold.
RESPIRATORY DISEASES: MEDICAL FACTORS
The medical factors which impact the development of all diseases, but show up particularly in respiratory infections are:
- Immunosuppression: people who are taking immunosuppressant drugs because of other medical treatments, such as cancer or transplants, are especially vulnerable to all infections.
- Reduced immune systems: people may not be on drugs which have a direct immunosuppression action, but be in a reduced state because of other long-term conditions, such as dialysis patients, or be in generally vulnerable heath, such as those with chronic long-term disabilities or conditions.
- Age: vulnerability to many infectious diseases increases with age. In any year, in the Western world, most of the people who die from widespread infectious diseases such as flu are elderly (over 80). This is also the group most likely to have contributing illnesses or conditions which reduce immune response.
The largest group who are vulnerable are the elderly. All other things being equal, the countries with the oldest population profile will show the highest death rates.
RESPIRATORY DISEASES: BEHAVIORAL FACTORS
The main behavioral impact on respiratory disease is smoking. In countries where smoking is still widespread, respiratory disease tends to have a bias to male smokers.
Smoking may have an age bias, but this is less clear-cut: where it is an ‘old’ habit, then more older people will be smokers and smoke more heavily, exacerbating vulnerability by age.
The new factor, however, is vaping. This is known to have a potentially injurious effect in countries where it has become popular. As vaping is a habit seen more in a ‘younger’ age group, this could create problems in an age group not usually seen as vulnerable.
Vaping of legal products may not be as harmful as smoking, but problems (and deaths) identified in the US are associated with the use of illegal products containing tetrahydrocannabinol (THC) (the psychotropic element in cannabis) which has been cut with a form of Vitamin E. This is known to cause so-called ‘popcorn lung’ which can be fatal.
Vaping is much more widespread in the US than other markets. Products, until recently, have been targeted at younger users, specifically though the use of sweet or fruit-flavored products and menthol products.
If the virus is seen to have a younger profile in the US than Europe, given that standard smoking is now no more common in the US than Europe, vaping could be a contributing factor.
RESPIRATORY DISEASES: ENVIRONMENTAL FACTORS
The main environmental factor with an impact on all forms of respiratory disease is air pollution.
Air pollution can come from a variety of sources, depending on which fraction is being examined, but general pollution is a combination of traffic exhausts (nitrogen oxides and particulates), road dust, industrial smoke and pollutants (including sulfur dioxide).
In some countries, domestic fires are a major source, especially if coal is used, and in a few countries, coal is a major fuel for power plants. Seasonal agricultural practices, such as stubble burning, can make a major contribution.
Whatever the source, air pollution load impacts people with reduced resistance, as can be seen in asthma and other disease statistics.
On top of general levels of pollution, some areas have a geographic susceptibility.
Many cities are built on bays or next to a big river. These are low-lying and some are surrounded by hills. This can create a ‘sink’ effect where polluted air becomes trapped and cannot escape in periods of calm weather. This can create both visible smog, and photo-chemical smog from gases such as nitrogen oxides.
In areas with a geographic susceptibility, calm weather can bring a rapid build-up in pollution (so-called ‘inversion’ where hotter, dirty air is trapped under cold, non-moving air).
Cities and urban regions which will be vulnerable to this include London, Paris, Los Angeles, the Ruhr and the Po Valley (see below).
WHY HAS ITALY BEEN SO HARD-HIT?
Italy has many world-class universities and medical schools which will undoubtedly be trying to track down why Northern Italy has been so hard-hit by COVID-19, so the following are respectfully suggested as possible contributing factors.
The area worst-hit is high income; although the region has a high population, most people live in relatively small cities and towns. The biggest city is Milan, followed by Turin and Venice/Veneto, none of which are large by European standards.
However, the Po Valley is the center of Italian industrial production, and is also very subject to a build-up of atmospheric pollution because of its geography. This can be seen in the maps which have traced the recent reduction of pollution due to the close-down in European production since February.
Italy also has the oldest population profile in Europe. Twenty-three percent of the population are over 65, and 12% are over 75. In parts of the northwest, the proportion is higher than average:
There is a long-standing connection between industrial companies in Italy and China, which may have played a role in introducing the virus before it was known to be dangerous: however, whether the degree of such contacts is greater than other parts of industrial Europe is less clear.
Smoking in Europe is now down to 20% of the population (daily smokers, plus 5% ‘occasional’). In Italy, smoking is lower than average at 17.8% daily smokers and 4.9% ‘occasional’. Older people smoke a lot less, and as in other parts of Europe, higher income groups are less likely to smoke than average.
There will be other factors, but it appears that smoking may not be a factor, however, atmospheric pollution, plus an older than average population, may be. This may not affect rates of infection, but lead to more serious illness when the infection is caught.
CHINA: SMOKERS AND ATMOSPHERIC POLLUTION
Overall, just under 28% of the population smokes in China, but this breaks down as almost no women (under 3%) and over half of men (52%).1
Local smoking rates are measured in the CCATS survey and do vary between cities and rural areas. Pollution is monitored regionally, but not necessarily published. At this sensitive time, data is not easy to access.
Source:
Parascandola M. and Xiao L. Tobacco and the lung cancer epidemic in China. Translational Lung Cancer Research (May 2019) 8(Suppl 1): S21–S30 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6546632/
